1. Field of the Invention
Exemplary embodiments of the invention relate to a liquid crystal display and a method of driving the same. Although the exemplary embodiments of the invention are suitable for a wide scope of applications, they are particularly suitable for preventing direct current (DC) image sticking and stains so as to increase the display quality.
2. Discussion of the Related Art
Active matrix type liquid crystal displays display a moving picture using a thin film transistor (TFT) as a switching element. The active matrix type liquid crystal displays have been implemented televisions as well as display devices in portable devices, such as office equipment and computers, because of the thin profile of the active matrix type liquid crystal displays. Accordingly, cathode ray tubes (CRT) are being rapidly replaced by the active matrix type liquid crystal displays.
If a DC voltage is applied to the liquid crystal display for a long time, image sticking map appear and stains may appear on the display screen of the liquid crystal display. If a DC voltage of the same polarity is applied to a liquid crystal layer for a long time, impurity ions in the liquid crystal layer are separated depending on a polarity of the liquid crystal. Further, ions with different polarities are respectively accumulated on a pixel electrode and a common electrode inside the liquid crystal cells. If a DC voltage is applied to the liquid crystal layer for a long time, the amount of accumulated ions increases. Hence, an alignment layer is degraded and alignment characteristics of the liquid crystal are degraded. In other words, the application of the DC voltage to the liquid crystal display for the long time may cause stains on the display screen. The development of a liquid crystal material with a low dielectric constant or a method for improving an alignment material or an alignment method have been attempted so as to solve the stain problem. However, it takes a long time and a heavy expense to develop a material used in the method. The use of the liquid crystal material with the low dielectric constant may reduce the drive characteristics of the liquid crystal. According to the experimental findings, as the amount of impurities ionized inside the liquid crystal layer increases and an acceleration factor becomes large, a time when the stains are revealed becomes rapider. The acceleration factor may include a temperature, time, DC drive of the liquid crystal, and the like. Accordingly, the stains may worsen at a high temperature or when the DC voltage of the same polarity is applied to the liquid crystal layer for the long time. Because the stains non-uniformly appear between panels manufactured through the same manufacture line, the stain problem cannot be solved only the development of new material or an improvement method of process. A method for suppressing the DC drive of the liquid crystal is effective in solving the stain problem.